Heavy Metal Contamination and Genotoxic Effects of Gold Mine Effluent on Allium cepa L. in Isanlu, Kogi State, Nigeria

Abstract

This study aimed at examining the level of heavy metals as well as the chromosomal abnormalities associated with effluent from the gold mine at Isanlu, Kogi State, Nigeria. Effluent from gold sluicing ore were collected at the point of washing and analysed for heavy metals. Onion (Allium cepa) roots were exposed to varying effluent concentrations (25%, 50%, 75%, and 100%) and analyzed for chromosomal abnormalities while those grown in distilled water serving as control, each treatment had three replicates. The heavy metals concentration in the gold mine wastewater is as follow; Cd (0.02), Cr (0.096), Cu (1.21), Fe (0.25), As (0.015), Ni (0.085), Zn (2.15), Pb (0.06), and Hg (0.0009) The order of abundance of the nine heavy metals in the effluent is as follows: Zn > Cu > Fe > Cr > Ni >Pb> Cd > As > Hg. Four heavy metals (Cd, As, Ni, and Pb) out of the nine analyzed occurred beyond WHO permissible level for effluent discharge. The study revealed that eight chromosomal aberrations which include bridged chromosome, fragmented chromosomes, variant chromosomes, C- mitotic cells, sticky chromosomes, spindle disturbance, binucleate cells, and vacuolated cells were induced in cells treated with different concentrations of the effluent. it was observed that all the concentrations produced negative relative division rates with 25%, 50%, 75% and 100% producing -23.26%, -5.08%, -18.01% and - 20.09% aside from the control. This revealed mito-suppressive effects of the effluent. Evidence from this study strongly indicated that the goldmine effluent is highly contaminated with heavy metals as well as genotoxic and mutagenic at every concentration.